An uninterruptible power supply (UPS) provides backup power to a load during loss of an input power source (typically termed a main power supply). UPS units typically include batteries that provide the backup power. During normal operation of a system that uses a UPS unit, an input power source provides power to the load and also charges the batteries of the UPS. During loss of input power, the batteries of the UPS provide power to the load. As a result, an uninterrupted supply of power can be provided to the load. Frequently, such a UPS may provide power for a sufficient time for the powered load to perform operations needed to power down smoothly, such as a computer finishing its current tasks and saving data from those tasks to permanent memory.